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Biology

If someone were to ask you what biology was, how would you reply? Biology is quite a complex concept to explain. Does it study plants, animals, and humans only, or does it cover much more than that?

StudySmarter’s Biology Revision and Notes will show you that biology is the study of life. In fact, it is the study of ALL life and even some things that are classified as not living – viruses, for instance. Biological study starts from the smallest atoms and molecules, such as carbon atoms in the proteins that digest our food. Biology then examines larger structures, such as tissue, organs, and whole organisms, including bacteria, viruses, plants, animals, and humans. It continues with the study of topics including genetic diversity, the evolution of species, and ecosystems.

Deep dive: Our planet Earth is one massive, incredible ecosystem! It is packed with various forms of life, from the smallest microorganisms to plants and large animals. These forms of life interact with one another; they move, reproduce, and live in oceans, grass, cities, villages, etc. Imagine you are standing on the top of a mountain, looking down at all this diversity. That is all included in the study of life, i.e. biology. Impressive, isn’t it?

Biology topics and learning objectives

On StudySmarter, you will find vital resources for your biology courses. We follow specifications developed by expert teachers of biology. This way, we ensure our content is high-quality and relevant to all who embark on a learning journey with StudySmarter. Most biology courses cover the following topics:

  • Biological molecules.
  • Cells.
  • Substance exchange.
  • Genetic information.

You’ll find those on StudySmarter, but we offer you these topics as well:

  • Energy transfers.
  • Responding to change.
  • Genetics, populations, evolution and ecosystems.
  • Control of gene expressions.

Let’s introduce all the biology topics.

Biology: Biological molecules

Biological molecules are carbon-based compounds essential for most biological processes.

Biological molecules serve as the structural components of molecules and cells, such as simple carbohydrates in bases of DNA and RNA and complex carbohydrate cellulose in plant walls. Moreover, biological molecules called lipids build cell membranes, forming a phospholipid bilayer. Some biological molecules, like proteins, act as enzymes, messengers and hormones, carrying out metabolic functions. Nucleic acids, DNA and RNA, carry the genetic information in all living things and viruses. The other two essential biomolecules are ATP (adenosine triphosphate) and water, necessary for cellular processes.

Biology simplified molecule diagram biological molecules StudySmarter

Simplified diagram of a molecule. Canva.com

Biology: Cells

Cells are the smallest units of life. The study of cells is one of the most significant in biology.

Cells can be either prokaryotic or eukaryotic. They contain genetic material and divide to create new cells. Eukaryotic cells divide with processes called mitosis and meiosis. Prokaryotic cells divide by binary fission.

Cells vary in the number and type of organelles, which are subunits inside all cells. One of the essential structural components of the cell is the cell surface or plasma membrane. It serves as a protective layer and is the main player in transporting vital substances in and out of cells.
Specialised cells called T lymphocytes and B lymphocytes are crucial for our immune systems. These cells aid in the fight against diseases.

Biology eukaryotic cells, animal and plant cell StudySmarter

Eukaryotic cells: an animal cell and a plant cell. Freepik.com/brgfx

Biology: Substance exchange

Substance exchange in biology is the exchange of substances (e.g. glucose) between the internal and external environments of cells. This is how organisms get oxygen and nutrients from the external environment and get rid of metabolic waste. Multicellular organisms require specialised organ systems for substance exchange because their surface area to volume ratio is too small to rely on cell membranes as an exchange surface.

Substance exchange in plants is called a mass flow system. The mass flow systems of plants comprise xylem and phloem. Substance exchange in animals happens in different organ systems, including the digestive, respiratory, and circulatory systems. Digestion and absorption of nutrients occur in the digestive system, whereas gas exchange takes place in the respiratory system. The circulatory system pumps and circulates blood that carries nutrients and oxygen. This role of the circulatory system is crucial to ensure the high metabolic activity of cells for all of the organ systems in the body to function properly.

Biology Human heart diagram StudySmarter

Diagram of the human heart. Smart.servier.com

Biology: Genetic information

DNA is a remarkable molecule consisting of our genetic material. Genetic material is involved in every aspect of biology, making DNA an essential molecule for the continuation of life.

The DNA in the nucleus is organised into genes made of nucleotides, which are found on chromosomes. Sometimes, the order of these nucleotides goes wrong, and mutations occur. Different mutations have different effects on the organism, but one of the beneficial effects is introducing genetic diversity into a species. Genetic diversity is also achieved during meiosis (a type of cell division) which allows DNA to be switched around so that the sex cells (also called gametes) have a different combination of DNA.

As a result of this vast genetic diversity in organisms, we have millions of species that we need to organise and classify. This is the study of taxonomy. Complementary to genetic diversity is the biodiversity we see in communities. We can quantify this level of diversity using measurements such as the index of biodiversity and species richness.

Biology DNA and RNA diagram StudySmarter

DNA and RNA. Smart.servier.com

Biology: Energy transfers

The term energy transfer refers to the changes in energy that occur in and between organisms within an ecosystem. All life depends on energy, which is usually derived from the Sun. The transfer of this energy between different organisms allows them to maintain their highly ordered environments and communities.

When it comes to how energy is transferred, there are two types of organisms: autotrophs, including plants, lichens or algae, and heterotrophs, including animals and humans. Most autotrophs gain energy from the Sun via photosynthesis. This process involves autotrophs using light energy to turn carbon dioxide and water into glucose and oxygen. Heterotrophs cannot synthesise their own energy and rely on acquiring it through consuming other organisms. They perform an inverse process to photosynthesis: they take glucose and oxygen and turn them into carbon dioxide and water. This energy transfer is called respiration.

Biology plant and sun, photosynthesis StudySmarter

Plants use the energy from the Sun for photosynthesis. Canva.com

Biology: Responding to change

Organisms respond to change in the internal and external environments. The change comes in the form of a stimulus. The stimuli (singular stimulus) can be a physical or chemical change and are recognised by specialised cells called receptors. The response to the stimuli is crucial for the survival of species.

Neurones or nerve cells are cells specialised for transporting nerve impulses. There are millions of neurones in mammals, making up the complex and fascinating nervous system. Some of the organs coordinated by the nervous system are the muscles. Contraction of skeletal muscles starts with an action potential reaching and travelling deep into muscle fibres, ultimately triggering the sliding filament mechanism.

All these responses to changes are necessary for the body to maintain a constant internal environment. This is called homeostasis. Living organisms require a consistent temperature, pH, and an overall chemical balance to function.

Biology Diagram of a synapse and the transmission of nerve impulses StudySmarter

Diagram of a synapse and the transmission of nerve impulses. Smart.servier.com

Biology: Genetics, populations, evolution and ecosystems

Individual members of one species have the same set of genes but can vary in combinations of alleles. Alleles are different forms of a gene responsible for the genetic diversity in species. The more alleles in the genome of a species, the greater the genetic diversity.

When members of one species live together in a habitat, they form populations. These, in turn, form communities where diverse species cohabit and interact with one another. The population size can vary and is affected by biotic (living) and abiotic (non-living) factors. For instance, competition and predation within or between different species are biotic factors, while the pH and temperature in the species’ habitat are abiotic factors.
Communities and the environment they inhabit make up ecosystems. An ecosystem is a self-sustaining, dynamic system that includes all living organisms (biotic part of the ecosystem) and the physical environment (abiotic components).

Biology A varied ecosystem with animals, plants, mountain and river StudySmarter

A varied ecosystem with animals, plants and their habitat. Freepik.com/macrovector

Biology: Control of gene expression

Some of the DNA in our cells can contain mutations. Considering all cells start off with the same genome, how can they have different functions and features, i.e. mutations? It is because of different levels of gene expression. Some genes in the genome are switched ‘on’, meaning they are expressed, and the proteins they code for are made, while other genes are switched ‘off’, meaning the corresponding protein is not synthesised.

Mutations can affect the level of expression, but epigenetics also plays a significant role. Epigenetics investigates the modifications made to DNA and their associated proteins and how this affects the level of gene expression. Other influencing factors include processes happening before transcription and before and after translation.

These investigations into DNA and genes require remarkable gene technologies, which have been used to develop advanced medical techniques such as gene therapy and forensic technology such as DNA profiling (genetic fingerprinting).

Biology A scientist investigating DNA and genes, biotechnology StudySmarter

A scientist investigating DNA and genes. Canva.com

How can StudySmarter support me in studying Biology?

Whether you are revising the topics covered in your biology course or studying for your upcoming exams, StudySmarter has got you covered. Our original, efficient, smart, and interactive learning system allows you to master biology like never before. What’s more, it’s all free!

What is the secret? How do we do it? To find out more, follow our Biology Revision Guide.

Biology support for biology exams, a group of friends talking about biology StudySmarter

The secret to passing biology exams. Freepik.com/pch.vector

The Biology Revision Guide

Our intelligent guide is here to introduce everything you need to know to revise your biology courses and exams successfully. Here is what you can discover on StudySmarter:

Biology summaries

StudySmarter biology summaries cover all you need to know about essential topics in biology, introducing interesting facts that will deepen your understanding and appreciation of the subject. Did you know that a human heart goes through a cardiac cycle that is only 0.8 seconds long?

You can also become a creator yourself by uploading your biology coursework: summaries, workbooks, notes, and more.

Biology flashcards

Flashcards are a fantastic feature helping you learn in an easy and fun way. Biology flashcards contain questions and answers on topics covered in the summaries. Did you know that you can create your flashcards with particular questions YOU want to practice? How cool is that!

Biology study groups

You don’t have to stop at creating and uploading your material. StudySmarter lets you form study groups and learn with your friends and biology students from wider learning communities. Remember the flashcards? You can use them to quiz fellow group members and test their knowledge. This way, you can create a personalised Biology quiz! Learn, create, quiz – repeat.

Rewards for learning Biology

StudySmarter is your next best friend, encouraging you to learn and achieve top results. StudySmarter lets you set your weekly goals: complete subjects, correctly answer flashcards, ask questions. Reaching these goals will earn you trophies. For example, gain the Best thing since sliced bread if you study every week for three months, or become a Grandmaster if you answer five questions in the same course. The more you learn, the more trophies you get to celebrate your hard work.

Final Biology Quiz

Question

Both DNA and RNA are _____ acids.

Show answer

Answer

Nucleic.

Show question

Question

Compare the functions of DNA and RNA.


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Answer

DNA stores genetic information while RNA transfers this genetic information for protein synthesis.

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Question

Where is DNA found in the cells of eukaryotes and prokaryotes?


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Answer

In eukaryotes, DNA is in the nucleus, mitochondria and chloroplast (in plants). 


In prokaryotes, DNA is in the nucleoid and plasmids.

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Question

Where is RNA found in the cells of eukaryotes and prokaryotes?


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Answer

In eukaryotes, RNA is in the nucleolus and ribosomes. 


In prokaryotes, RNA is in the nucleoid, plasmids and ribosomes.

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Question

Identify the three different types of RNA.


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Answer

Messenger RNA (mRNA), transfer RNA (tRNA) and ribosomes RNA (rRNA).

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Question

What nitrogenous bases can DNA nucleotides have?


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Answer

Adenine, thymine, cytosine or guanine.

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Question

What nitrogenous bases can RNA nucleotides have?


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Answer

Adenine, uracil, cytosine and guanine.

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Question

Identify the pyrimidine and purine bases. 


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Answer

The pyrimidine bases are cytosine, uracil and thymine. 


The purine bases are adenine and guanine.

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Question

DNA contains the _____ pentose sugar while RNA contains the _____ pentose sugar. 


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Answer

Deoxyribose. 

Ribose.

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Question

________ reactions form polynucleotides while _____ reactions break polynucleotides. 

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Answer

Condensation. 

Hydrolysis.

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Question

What are phosphodiester bonds and how are they formed?


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Answer

Phosphodiester bonds link nucleotides together. They are formed between the phosphate group of one nucleotide and the hydroxyl group at the 3 'pentose sugar of another nucleotide.

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Question

Compare the structure of a DNA and RNA molecule. 


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Answer

DNA is an anti-parallel double helix made of 2 polynucleotide strands while RNA is a single-stranded molecule made of 1 polynucleotide strand.

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Question

What is complementary base pairing? 


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Answer

Complementary base pairing is the joining of a pyrimidine base to a purine base via hydrogen bonds.

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Question

In complementary base pairing, how many hydrogen bonds are formed between the base pairs?


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Answer

Adenine forms 2 hydrogen bonds with thymine in DNA, or uracil in RNA. 


Cytosine forms three hydrogen bonds with guanine.

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Question

DNA and RNA are polynucleotides. The monomers that make up these polynucleotides are called _____.

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Answer

Nucleotides.

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Question

Substance exchange in multicellular organisms occurs solely via diffusion. (True/ False)

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Answer

​​​​False - the surface area to volume ratio of multicellular organisms is too small for substance exchange to occur via diffusion. Instead, multicellular organisms have mass transport systems adapted for this function


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Question

Stomata, singular stoma, are located on the underside of leaves. (True/ False)


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Answer

True

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Question

Name the process where water from plants is inevitably lost when stomata are opened for gas exchange.


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Answer

Transpiration

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Question

Do plants also require oxygen? Describe the adaptations of plants in maximising the absorption of oxygen.


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Answer

Plants also require oxygen for respiration. Leaves have sufficient oxygen because it is a byproduct of photosynthesis. Other plant parts adapt to maximising the absorption of oxygen by branching and having air spaces between cells. These adaptations serve to increase the surface area of plants to facilitate the diffusion of oxygen.


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Question

Translocation is the term used to describe mass flow in the phloem only. (True/ False)


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Answer

False - translocation is the term used to describe mass flow in BOTH the xylem and phloem


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Question

The xylem transports water, whereas the phloem transports substances made by photosynthesis (True/ false). 


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Answer

True

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Question

Briefly explain why animals have a circulatory system that consists of a pump-like organ (heart) and more complex vessels for substance exchange.


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Answer

Animals have greater metabolic demands. Thus, circulatory systems serve to maximise the efficiency of substance exchange.

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Question

Fill in the blanks.

The gas exchange surfaces in fish are composed of structures called ____ that are divided into ______ that contain many ______.


Gas exchange occurs in the _____ which follow the ____________ ______. This means that ____ and _____ inside flow in ______ directions.

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Answer

The gas exchange surfaces in fish are composed of structures called gills. Gills are divided into filaments that contain many lamellae.


Gas exchange occurs in the lamellae, which follow the counter-current system. This means that the blood and water inside flow in opposite directions.

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Question

Instead of capillaries, gas exchange in insects occurs in the trachea as they form direct contact with respiring cells. (True/ False)


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Answer

True

Show question

Question

Outline how the alveoli are adapted for gas exchange.

 

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Answer

The alveoli are adapted for gas exchange via their thin (i.e. one cell thick) walls and close proximity with capillaries.

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Question

The heart is made up of specialised muscle cells that contract voluntarily (True/ False)

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Answer

False - the heart is made up of specialised muscle cells that contract INVOLUNTARILY


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Question

Multicellular organisms have a large surface area to volume ratio (True/ False)


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Answer

False - multicellular organisms have a SMALL surface area to volume ratio

Show question

Question

Fill in the blanks.

Multicellular organisms require circulatory systems due to their _____ surface area to volume ratio. Therefore they cannot rely on _____ alone like unicellular organisms (e.g. yeasts) for the exchange of substances. This is because their large _____ require substances to travel large ______ to enter. Subsequently, the surface for substances to enter proportionately______, ultimately becoming too _________if diffusion is the only means of exchanging substances .


Animals need a _____ because of their high metabolic rate necessary for generating sufficient energy (ATP). As animals are unable to ______ like plants, they have the capacity for _______ to obtain food. A biological pump is then essential for maximal _____ of the exchange of metabolic substances across cells.

Show answer

Answer

Multicellular organisms require circulatory systems due to their small surface area to volume ratio. Therefore they cannot rely on diffusion alone like unicellular organisms (e.g. yeasts) for the exchange of substances. This is because their large sizes/volumes require substances to travel large distances to enter. Subsequently, the surface for substances to enter proportionately reduces, ultimately becoming too time-consuming if diffusion is the only means of exchanging substances.


Animals need a heart because of the high metabolic rate necessary for generating sufficient energy (ATP). As animals are unable to photosynthesise like plants, they have the capacity for locomotion to obtain food. A biological pump is then essential for maximal efficiency of the exchange of metabolic substances across cells.


Show question

Question

Double circulatory systems are found in organisms where oxygen demand is low (True/ False)

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Answer

False - single circulatory systems are found in organisms where oxygen demand is low

Show question

Question

Venules are a type of blood vessel (True/ False)


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Answer

True

Show question

Question

The circulatory system produces hormones such as insulin (True/ False)


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Answer

False - insulin is produced in the pancreas, the circulatory system TRANSPORTS insulin to target cells

Show question

Question

What is the definition of biological molecules?


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Answer

Biological molecules are fundamental building blocks of all living things.


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Question

What kind of molecules are biological molecules?

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Answer

Biological molecules are organic molecules, meaning they contain carbon and hydrogen. 


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Question

All biological molecules are organic. 

True or False.

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Answer

False. Water is an example of an inorganic biological molecule. 

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Question

What are the three chemical bonds in biological molecules?


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Answer

Covalent, hydrogen, and ionic bonds.


Show question

Question

Which bond is the most commonly found in biological molecules?
Choose a correct answer.     

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Answer

Covalent

Show question

Question

What kind of covalent bonds form when there is an uneven distribution of electrons?


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Answer

A polar covalent bond.


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Question

How many covalent bonds can a carbon atom form?


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Answer

​4

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Question

What are the four major biological macromolecules?


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Answer

The four major biological macromolecules are: 

  • carbohydrates
  • lipids
  • proteins 
  • nucleic acids: DNA and RNA.

Show question

Question

What are the different types of carbohydrates?


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Answer

Monosaccharides, disaccharides, and polysaccharides.


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Question

What is the covalent bond between monosaccharides called?

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Answer

A glycosidic bond.

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Question

What are the building blocks of lipids?

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Answer

Fatty acids and glycerol

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Question

What are the two major types of lipids?

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Answer

Triglycerides and phospholipids.

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Question

What is the covalent bond in lipids called?

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Answer

An ester bond.

Show question

Question

What are the four different protein structures?

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Answer

Primary, secondary, tertiary, and quaternary. 

Show question

Question

The covalent bond between amino acids is called a phosphodiester bond. True or False

Show answer

Answer

False. It is called a peptide bond. 

Show question

Question

What are monomers of nucleic acids called?

Show answer

Answer

Nucleotides. 

Show question

Question

What are the two types of nucleic acids?

Show answer

Answer

DNA and RNA

Show question

Question

What is the covalent bond between nucleotides called?

Show answer

Answer

A phosphodiester bond. 

Show question

Question

Outline the four different functions of circulatory systems.

Show answer

Answer

  • supply respiring cells with nutrients such as glucose (e.g. from small intestines to respiring tissues)
  • maintain a constant supply of oxygen to cells undergoing aerobic respiration (e.g., from lungs to respiring tissues)
  • rid metabolic waste products (e.g., carbon dioxide in respiring tissues back to the lungs)
  • transporting substances made from one part of the body to another (e.g., hormones such as insulin made in the pancreas to muscle cells)

Show question

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